Dural defect is a common problem during neurosurgery. Open craniocerebral injuries (industrial, traffic or war-related), tumor invasion, congenital meninges defects or other cranial diseases can lead to defects of the dura mater. Such defects of the dura mater need be repaired timely so as to prevent leakage of the cerebrospinal fluid, encephalocele, and stress from the barometric pressure. Otherwise, it can be life endangering.
Currently, although there are many dura substitutes, materials used in the substitutes can be generally classified into four types: autologous fascia, allograft, natural or synthetic substance, and xenograft. However, clinical application of these materials unavoidably leads to problems such as high infection rates. According to statistics, the infection rate for craniotomy is 4%; the dura mater made of pig's small intestine mucosa gives an infection rate of 3.4%; and the dura mater manufactured by collagen exhibits an infection rate at 3.8%. Because of the blood brain barrier, once intracranial infection occurs, the encephalic plasma concentration of anti-infection drugs can hardly reach the desired level and control of infection becomes difficult. Also, the existing artificial dura products do not have the capability of supplying medicines into the meninges. Therefore, post-operation infection control is often ineffective.
Moreover, one of the common reasons for dural repair with dura mater transplant is damages to the meninges due to tumor invasion. More than half of brain tumors cannot be completely removed by surgery and thus chemotherapy is necessary after the surgery. Many chemotherapeutic drugs are toxic and cannot pass the blood brain barrier, so that an effective concentration of the drugs cannot be reached resulting in diminished chemotherapy effects.
Current artificial dural substitute products usually do not contain therapeutic drugs of interest. For instance, due to the dense structures, the autologous fascia can not be loaded with drugs naturally, and it is difficult to load drugs into allograft or xenograft. However, due to their good malleability, synthetic material-based dural substitutes can be readily loaded with drugs. On the other hand, due to the limitation of loading methods of a drug, it is also not easy to load the drug onto artificial dura mater, and yet allow release of the drug upon transplantation to achieve therapeutic objectives. To date, the common way to load an anti-infection drug onto an artificial dura mater substitute is to soak the substitute with the drug. With this method, most of medicine remains on the surface of artificial dura mater, which is easily lost, making it difficult to achieve controlled release.
It is apparent, therefore, that current artificial dura mater substitutes have shortcomings. Among these are a high infection rate, poor bio-compatibility, incomplete absorbability, and difficulty in loading medicine and controlling the effective release of the medicine.